Ni-based alloy brazing filler materials superior in corrosion resistance and oxidation resistance have been conventionally used for brazing stainless steel. In particular, BNi-2 (Ni—Cr—Fe—B—Si alloy), BNi-5 (Ni—Cr—Si alloy) and BNi-7 (Ni—Cr—P alloy) defined in JIS Z 3265 (1998) are frequently used. The above three types of Ni-based brazing filler materials respectively has an advantage as well as a disadvantage and is thus used differently depending on application.
For example, BNi-2 has a relatively low liquidus-line temperature of about 1000° C. while its corrosion resistance is not necessarily sufficient. BNi-5 is superior in corrosion resistance while its liquidus-line temperature is about 1140° C., which necessitates a high brazing temperature. In addition, BNi-7 has an extremely low liquidus-line temperature of about 900° C. and a relatively good corrosion resistance, while having to use a Ni—P alloy raw material, which is relatively less available to raise a supply concern, for the purpose of adding phosphorus (P). In this way, since there is no Ni-based brazing filler material having a low liquidus-line temperature and a superior corrosion resistance and comprising a raw material that is relatively easily available, there has been a need for developing a new alloy brazing filler material.
To these problems, there has been proposed, for example in JP09-225679 (Patent Literature 1), a Ni-based heat resistance brazing filler material having a low liquidus-line temperature and a high corrosion resistance. This Ni-based heat resistance brazing filler material is a superior alloy having a low liquidus-line temperature by defining the additive amount of Cr for providing a high corrosion resistance as well as by defining the additive amounts of P and Si that exhibit a eutectic reaction with a Ni—Cr solid solution, while on the other hand necessitating Ni—P that is relatively less available as raw material.
In addition, JP2009-148769A (Patent Literature 2) discloses an alloy that enables a significant reduction in raw material cost by having the base alloy itself composed of Fe and Cr that are very inexpensive instead of Ni that is relatively expensive, while the liquidus-line temperature is 1060° C. or higher as described in its Examples.